Data Science

Range, IQR, Variance, and Standard Deviation - Measures of Spread

Arun Murali

Tags: data-science; statistics; descriptive-statistics

🟪 1-Minute Summary

Measures of spread tell you how dispersed your data is. Range (max - min) is simple but sensitive to outliers. IQR (interquartile range) is robust. Variance measures average squared deviation from the mean. Standard deviation is the square root of variance and shares the same units as your data, making it most interpretable.

🟦 Core Notes (Must-Know)

Range

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Interquartile Range (IQR)

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Variance

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Standard Deviation

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When to Use Each

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🟨 Interview Triggers (What Interviewers Actually Test)

Common Interview Questions

  1. “Why do we square the differences when calculating variance?”

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  2. “What’s the advantage of standard deviation over variance?”

    • [Answer: Same units as original data]

🟥 Common Mistakes (Traps to Avoid)

Mistake 1: Forgetting to take square root for standard deviation

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🟩 Mini Example (Quick Application)

Scenario

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Solution

import numpy as np

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🔗 Related Topics

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